Based on investigation data on PHC in Jiaozhou Bay,China from 1979 to 1983,the monthly,seasonal and annual variations of PHC content in Jiaozhou Bay were studied.The results showed that from 1979 to 1983,Jiaozhou Bay was polluted by PHC seriously and then slightly in spring and summer,while Jiaozhou Bay was polluted by PHC slightly in autumn.During 1979-1983,PHC content in the water body of Jiaozhou Bay decreased year by year,and it was close to the background value gradually.Moreover,the reduction was obvious in spring and summer but very slight in autumn.Therefore,the water quality of Jiaozhou Bay became better.